The present invention relates to a film feeding control device for camera.
Various methods have been known heretofore in which a film loaded in a camera is fed frame by frame for each completion of photographing. In one of these methods, a sprocket is provided to engage with the perforations located on the side of a film, and the film is fed frame by frame by turning the sprocket by a specified angle through film advance operation.
On the other hand, an electrically film-winding type a camera has recently been commercially available in which film winding is performed by motor drive, not by manual operation. Such camera employs a method in which the feed of one film frame is controlled by detecting optically the number of perforations.
That is, the method is such that a film feeding path is provided with a photointerrupter in which a light beam is applied to the position through which the perforations pass and the reflection or permeation of the beam is optically detected, and the resultant output is compared with a predetermined threshold limit value and then a motor is allowed to stop based on the compared result so as to control the feed of one film frame (for example, Japanese Pat. laid open No. 2296/1987).
However, where a reflection type photointerrupter is used in such feeding control systems, a different reflection coefficient due to individual film properties or a change of the supply voltage to the photointerrupter with a decrease of battery voltage causes the output of the photointerrupter to be changed, so that the setting of the threshold limit value may become difficult or in some case become impossible.